No Money. - Videos let me watch games that aren't worth buying to me along with letting me parse games that look fun enough to buy.
No Time. - Videos can be put on during other chores or tasks, left on as background noise during times where I would absolutely not have enough time to actually play a game.
Skill Issue. - No matter how good I want to be, I'm ultimately just kinda ok at games. Watching higher level players can be a way for me to learn tips and tricks to improve, or they can be a way for me to experience difficulty levels of the game I will never realistically achieve on my own.
You forgot: The videos often have absurd challenges that most gamers would never try, like for example trying to beat Pokemon Ruby and Sapphire with only a physical attacking Abra.